Ignition Diagnostic Monitor (IDM)

PURPOSE
The Ignition Diagnostic Monitor (IDM) is a function of the Powertrain Control Module (PCM). Information on system failures is stored within the PCM and used for diagnostic self-tests.


OPERATION
The IDM signal is transmitted on each spark firing. This signal communicates information by pulse width modulation and provides a clean buffered signal with a frequency proportional to engine speed for tachometer operation.